Programmed Delay of a Virulence Circuit Promotes Salmonella Pathogenicity

Area of Science:

• Microbiology
• Molecular Biology
• Pathogenesis

Background:

• Signal transduction regulates cellular responses to environmental cues.
• The PhoP/PhoQ system is crucial for Salmonella virulence within host cells.
• Pathogens require precise timing of virulence gene expression for infection.

Purpose of the Study:

• To investigate the mechanism by which Salmonella delays the activation of the PhoP/PhoQ virulence system.
• To identify regulatory factors controlling virulence gene expression timing in Salmonella.

Main Methods:

• Investigated the role of EIIA^Ntr in regulating PhoP/PhoQ activity.
• Assessed the impact of acidic pH on EIIA^Ntr and PhoP interactions.
• Analyzed PhoP binding to target promoters in the presence of EIIA^Ntr.

Main Results:

• EIIA^Ntr inhibits PhoP binding to its target promoter, delaying virulence gene expression.
• Salmonella degrades EIIA^Ntr at acidic pH in a Lon- and PhoP-dependent manner.
• This degradation allows for robust activation of the PhoP-regulated virulence program.

Conclusions:

• Salmonella employs EIIA^Ntr as an inhibitory protein to control the timing of virulence gene activation.
• Programmed delay of virulence ensures efficient and coordinated infection by Salmonella.
• Understanding this regulatory mechanism provides insights into pathogen survival strategies.